Alzheimer's Disease (AD) is a progressive, degenerative disease that affects the brain resulting in impaired thinking, uncharacteristic behavior and memory loss. The disease manifests in the degeneration of nerve cells responsible for memory and thought processes. AD has two physiological hallmarks: (1) bundles of largely insoluble plaques of beta-amyloid that develop in areas of the brain responsible for memory and cognitive functions and (2) neurofibrillary tangles, or abnormal collections of twisted threads inside nerve cells. The ultimate cause of the disease remains unknown. Therefore, the diagnosis of AD can only be completely confirmed by examination of brain tissue following death to determine whether the levels of plaques and tangles in certain brain regions are characteristic of AD. Because there is no cure for AD, early diagnosis of AD is critical for patients in giving them the benefit of drug therapies that may alleviate more moderate, early symptoms of AD and enhance their quality of life. Early diagnosis allows for the most effective treatment, medical and social management, and personal and family planning.
In diagnosing AD, physicians employ a battery of diagnostic tests, including a complete medical history, physical exam, blood and urine analysis, and memory and psychiatric assessment, such as the Wechsler Memory Test and the Mini Mental State Examination. Assessment of olfactory function is employed in diagnosing AD. The patients exhibit signs of olfactory dysfunction even before the patients manifest other symptoms of AD. Differential olfactory performance recognized between healthy and affected patients, along with lack of awareness of olfactory deficit, provide a mechanism for early screening and diagnosis of AD. Studies suggest that assessment of olfactory function is more reliable than standard cognitive capacity tests, and that diminished sense of smell, along with other factors, such as memory loss and genetic factors, provides the best indicator of AD.
Two principal methods are used to clinically evaluate olfactory function. In one method, vials of scented liquids, each with a distinct scent, are used to assess the examinee's sense of smell. A complete test kit requires several vials of liquid. The second method involves test cards with distinct odor strips affixed to each card. Odor is released when scented microcapsules within each strip are ruptured. Rupture is accomplished either by scratching the surface of the strip or by removal of an adhesive securing the strip to the card. Examples of such tests include the 40-item University of Pennsylvania Smell Identification Test (UPSIT) and the 12-item Cross-Cultural Smell Identification Test (CC-SIT).
Both principal methods are designed for general evaluation of olfactory function. The vial test is reused until the scent diminishes. The vial test requires a health care professional, such as a physician or nurse practitioner, to administer and score the test and then read and interpret the results. The test card method may be self-administered, but a healthcare professional must still score the test and then read and interpret the results. Both the vial test and test card methods are designed for and dependent on the active involvement of a healthcare professional to screen and interpret the resulting score for indications of neurological disease.
In the prior art tests, the required involvement of a healthcare professional has a number of disadvantages. The involvement of a healthcare professional significantly increases the cost to an individual desiring screening. Additionally, visits to a healthcare professional require a considerable time commitment. Furthermore, individuals may perceive mandatory professional involvement as an invasion of privacy. Finally, anxiety and trepidation are often associated with visiting a professional to assess neurological disease. Individually or in combination, these factors can easily dissuade a possible sufferer of neurological disease from early screening and diagnosis. As a result, many individuals will deny themselves the benefit of a useful diagnostic tool.